1. Field of the Invention
The present invention relates to a controller of a pressure accumulation fuel system.
2. Description of Related Art
A common rail fuel injection system is practically used as a fuel injection system of a diesel engine. The common rail fuel injection system accumulates fuel in a common rail at high pressure corresponding to fuel injection pressure and supplies the accumulated high-pressure fuel to the engine through a fuel injection valve. In the common rail fuel injection system, the fuel pressure in the common rail decreases if the fuel injection valve performs the fuel injection. At that time, the fuel supply pump supplies the high-pressure fuel to the common rail to maintain the inside of the common rail at a predetermined high-pressure state.
In the high-pressure fuel system using the common rail and the like, there is a possibility that fuel temperature increases in accordance with a change in an engine operation state and the like. A failure can be caused if the fuel temperature increases over allowable temperature of various components. Therefore, a countermeasure is necessary. However, addition of a cooler for inhibiting the increase of the fuel temperature is inadvisable.
A technology of sensing the fuel temperature and of preventing the fuel temperature from exceeding a predetermined value by restricting a fuel injection amount of the fuel injection valve, the discharge amount of the fuel supply pump, the fuel pressure in the common rail and the like is proposed, for example, as described in JP-A-H10-54267. The technology restricts the fuel injection amount, the fuel pressure or the like simply based on the fuel temperature. Therefore, there is a possibility that the fuel injection amount is restricted and torque is reduced when high torque is required by a driver. In such a case, the requirement of the driver cannot be satisfied, deteriorating drivability of a vehicle.
The fuel injection valve employs a structure of a two-way electromagnetic valve or a three-way electromagnetic valve. The high-pressure fuel is supplied or discharged (leaked) in accordance with opening operation and closing operation of the two-way electromagnetic valve or the three-way electromagnetic valve. A valve member moves in accordance with the leakage of the high-pressure fuel. Thus, the fuel injection is performed. In such a structure, there is a possibility that the fuel temperature rapidly increases in the leaking period of the high-pressure fuel and the fuel injection valve is damaged due to the increase of the fuel temperature.